// @import 'small.css' screen and (min-width:375px);
// @import url(big.css) screen and (min-width:768px);

body{
    @media screen and(min-width:375px) and (max-width:667px){
        background-image: url('https://source.unsplash.com/user/erondu/400x200');
        background-repeat: no-repeat;
        background-size: cover;
    }
    @media screen and(min-width:768px) {
        background-image: url('https://source.unsplash.com/user/erondu/800x800');
        background-repeat: no-repeat;
        background-size: cover;
    }
}